| 1 | Inflorescence terminal, sometimes also axillary to form a terminal panicle |
| 1' | Inflorescence axillary |
| 2 | Corolla tube mostly glabrous or with few hairs outside |
| 2' | Corolla tube densely pubescent outside |
| 3 | Corona lobes fused at base forming a tube in the corolla throat; stamens inserted at 0.4-0.6 of tube length |
| 3' | Corona lobes free or only slightly fused in pairs, not in a ring; stamens inserted at 0.2-0.3 of tube length |
| 4 | Corolla lobes 0.6-1 times as long as wide (see note above) |
| 4' | Corolla lobes 1.6-4.4 times as long as wide (see note above) |
| 5 | Sepals rounded |
| 5' | Sepals obtuse to acute |
| 6 | Secondary veins 40-60 pairs, almost perpendicular to midrib; corolla lobes with a squarish basal portion and a long caudate apex |
| 6' | Secondary veins 8-28 pairs, mostly not almost perpendicular to midrib; corolla lobes narrowly elliptic or strongly falcate with a projection to the side |
| 7 | Corolla lobes narrowly elliptic, 3.2-6.1 times as long as wide (see note above) |
| 7' | Corolla lobes strongly falcate with a projection to one side, 0.6-0.8 times as long as wide (see note above) |
| 8 | Corolla lobes 1.5-2 mm wide (measuring the projection as part of the width), apex of projection mostly fimbriate; tube 2.8-5.5 mm long, sparsely to densely pubescent around stamens inside; bud head about as long as wide with an obtuse apex. — Western Malesia |
| 8' | Corolla lobes 2.7-3.8 mm wide (measuring the projection as part of the width), apex of projection mostly not fimbriate; tube 5.2-12 mm long, glabrous or sparsely pubescent around stamens inside; bud head longer than wide with an acute apex. — New Guinea |
